1. Field of the Invention
The present invention relates to a flux-cored wire for gas shielded arc welding, which is used for welding of buildings, bridges, ships, and other various steel structures. More particularly, it relates to a flux-cored wire for gas shielded arc welding, which provides high welding workability including a very good arc condition and less spatter in welding of high heat input and high interpass temperature.
2. Description of Related Art
Conventionally, wires for gas shielded arc welding are classified into two types: a solid wire and a flux-cored wire.
For the solid wire for arc welding, various types of wires in which the components are controlled according to the purpose for use have been developed, and are generally used by being standardized in JIS Z3312 and other standards. The flux-cored wire for arc welding is classified into two groups: a generally called slag-based wire in which slag components are mainly filled and a generally called metal-based wire in which metal components are mainly filled. The flux-cored wire has been standardized in JIS Z3313 and other standards, and many kinds of flux-cored wires suited to various purposes have been developed.
However, since the solid wire is a metal wire, even if it is desired to contain a minute amount of an arc stabilizer to further improve the welding workability, the arc stabilizer cannot be contained.
On the other hand, the flux-cored wire can achieve high welding workability by the improvement in flux filled in the wire, so that many kinds of wires with high welding workability have been used practically. Almost all of the wires have a flux filling percentage of 10 to 20%. Although the disclosures of technology regarding a wire with a low filling percentage of 5% have been found sometimes, the wire with such a low filling percentage has problems of an excessive amount of welding slag, an excessive amount of fume generated, and the like. Actually, therefore, the wire with such a low filling percentage has not been supplied practically. Of the flux-cored wires, the metal-based flux-cored wire, which mainly contains metal powder to give welding workability as high as that of the solid wire, actually has problems of arc stability and productivity.
As described above, these types of wires have both merits and demerits. Therefore, a small-diameter wire for gas shielded arc welding, in which the merits of both solid wire and flux-cored wire are adopted, is desired.
For the flux-cored wire, a flux-cored wire with a low flux filling percentage, for example, filled with flux in the range of 5 to 25% in terms of percentage of cross-sectional area of wire has been disclosed in Japanese Patent Publication No. 51-1659. This Publication describes an example in which the flux filling percentage is as low as 5%, and has disclosed a wire filled with flux containing an indispensable component of graphite as an arc stabilizer, containing Ti, Al, Mg, etc. with a compounding ratio of 2 to 10%, and further containing 20 to 90% of a deoxidizer with no metal oxides being contained substantially. However, the arc stabilizer containing graphite is a cause for arc instability caused by CO reaction of the graphite with oxygen in wire or oxygen adhering to the wire surface, and provides coarse arc, so that the welding workability is deteriorated, and the amount of spatter generated is increased. Also, the content of C yielded in weld metal becomes excessive, so that the control of physical properties of weld metal is not easy.
Also, Unexamined Japanese Patent Publication No. 6-218577 has disclosed a flux-cored wire filled with flux containing 40 to 60% of a deoxidizer consisting of iron alloy powder of 40 to 60% of iron powder and Si, Mn and Ti, in which the content of Mn and S and the Mn/S ratio are restricted, and the flux filling percentage is 5 to 30%. This wire belongs to a metal-based flux-cored wire. For the wire with a filling percentage of 5% to 10%, a sufficiently stable arc cannot be obtained by the flux containing this metal powder, so that high welding workability and a satisfactory welding result as the flux-cored wire cannot be obtained.
An object of the present invention is to provide a flux-cored wire for gas shielded arc welding, which has merits of both solid wire and flux-cored wire, the merits being high depositing properties and a small amount of slag generated of solid wire and stable welding workability of flux-cored wire.
The inventors have solved a problem of arc stability by promoting the release of globules at the time of welding, decreasing the sizes of globules, and increasing the number of transfers of globules by containing an arc stabilizer containing a synthetic material consisting of Na2O and TiO2 and/or a synthetic material consisting of Na2O, SiO2 and TiO2 in a deoxidizer consisting of Si and Mn, and have solved problems of low deposition efficiency, shallow welding penetration, a large amount of slag generated, etc., which are drawbacks of the flux-cored wire, by decreasing the flux filling percentage to 3 to 10%. Thereupon, we have obtained an knowledge that the flux-cored wire is a very effective means for an entirely new flux-cored wire for arc welding, and thus have completed the present invention.
The present invention relates to a flux-cored wire for gas shielded arc welding and, more particularly, to a wire in which flux is filled in a steel sheath. A first mode of the present invention provides a flux-cored wire for gas shielded arc welding, in which flux is filled in a steel sheath, containing 0.3 to 1.8% (total wire mass percentage, the same rule applies to the following) of Si, 0.8 to 4.0% of Mn, and 0.15 to 2.0% of a synthetic material containing Na2O and TiO2 and/or a synthetic material containing Na2O, SiO2 and TiO2 as an arc stabilizer, with a flux filling percentage of 3 to 10% by mass.
A second mode of the present invention provides the flux-cored wire for gas shielded arc welding defined in the above-mentioned first mode, in which the filling flux contains 0.3% or less of Na2O source on a Na2O conversion value basis and/or 1.5% or less of TiO2 and/or the source on a TiO2 conversion value basis, in addition to the synthetic material containing Na2O and TiO2 or the synthetic material containing Na2O, SiO2 and TiO2.
A third mode of the present invention provides the flux-cored wire for gas shielded arc welding defined in the above-mentioned first mode, in which the wire further contains 0.02 to 0.15% of C, 0.02 to 0.3% of Ti, and 0.001 to 0.01% of B on a basis of total wire mass percentage.
A fourth mode of the present invention provides the flux-cored wire for gas shielded arc welding defined in the above-mentioned third mode, in which the wire further contains one or two and more kinds of 0.7% or less of Mo, 1.75% or less of Ni, and 1.0% or less of Cr on a basis of total wire mass percentage.
Furthermore, the present invention provides a flux-cored wire for gas shielded arc welding in which iron powder is contained in the filling flux.
Also, the present invention provides the above-described flux-cored wire for gas shielded arc welding in which the steel sheath has no butt or has a butt.
Also, the present invention provides the above-described flux-cored wire for gas shielded arc welding in which the steel sheath is copper plated or is not plated.